Formwork Pressure of a Heavyweight Self-Compacting Concrete Mix

Abstract

High-fluidity and self-compacting concrete (SCC) mixes were developed using special aggregates for radiation-shielding concrete. The special aggregates comprised heavyweight and hydrous aggregates (crushed magnetite, crushed serpentine, and their mixtures), which were selected to provide an enhanced attenuation of gamma and neutron radiation, respectively. For the mixed concrete design with a bulk density of up to 3570 kg/m3, two cement types were used: Portland cement CEM I and slag cement CEM III/A. The basic properties of the fresh self-compacting concrete were evaluated and the lateral formwork pressure exerted by the freshly mixed self-compacting concrete was measured and analyzed. An original test setup was developed for the determination of the lateral pressure on the square column formwork with pressure measurements carried out using six strain gauge pressure transducers, which was adequate for heavyweight concrete mixture testing. Self-compacting concrete mixtures containing a magnetite aggregate or blends of serpentine and magnetite aggregates with a slump flow of at least 550 mm were developed. The lateral pressure on the formwork was directly proportional to the density of the self-compacting heavyweight concrete mixes. The maximum values of the lateral pressure recorded in the test at a casting speed of 1.5 m/h did not exceed 27 kPa and 55% of hydrostatic pressure. Concrete mixtures with basalt, magnetite, and magnetite/serpentine blended aggregates were found to develop sufficient shear strength for proper stability during casting.

Relationship of Different Properties from Non-Destructive Testing of Heavy Concrete from Magnetite and Serpentinite

“…Our choice of materials for radiation-shielding concrete was based on a published study [ 10 ]. The choice of special aggregate—i.e., magnetite and serpentinite in different fractions—was governed by its basic properties; namely, the high atomic number.…”

“…Another important factor is the choice of cement. Two types of cement were selected for the study [ 10 ]—namely, Portland cement CEM I 42.5 N, and slag cement CEM III/A 42.5 N, following EN 197-1 [ 25 ]. These two types of cement have high resistance to initial cracking and long durability, due to low heat of hydration, resistance to sulfates, and low alkali content [ 26 ].…”

“…The columns were demoulded after 3 days and then stored in laboratory conditions at a temperature of 20 °C and 40% humidity for two years. The results of the elementary tests and the rheological properties were deeply evaluated in an already-published article [ 10 ].…”

“…Some studies show chromium-ore-based concretes containing various types of minerals [ 3 ] or other additives [ 4 , 5 , 6 ], as well as considering their ecological and sustainability aspects, such as in terms of recycling [ 7 ]. Others examine magnetite and serpentinite concretes [ 8 , 9 , 10 ], and their advantages and disadvantages.…”

“…The preparation of high-quality heavy concrete carries many difficulties that need to be researched in the long term [ 20 ]. In the first part of the research, the basic properties of heavy self-compacting concrete (SCC) mixtures were investigated, as well as the effect of high weight on formwork [ 10 ]. These concretes have been shown to have good radiation-shielding properties, and the proposed formwork solution has shown to be sufficiently load-bearing and stable.…”